Pressurized metered dose inhalers (pMDI) are commonly used by patients for self-administered treatment of respiratory diseases, such as asthma and chronic obstructive pulmonary disease (COPD). The pMDIs are versatile because they are adaptable for filling with various propellants, and dry or liquid medicaments. They are also convenient, since they are easily portable. However, despite regular use of the pMDIs, patients often experience serious respiratory distress that can be life-threatening. This is in part because patients are sometime unaware they have depleted the medication in their pMDIs and instead self-administer the propellant. Patients cannot visually monitor the amount of medication remaining in their pMDIs because the metal canisters are not transparent. And most pMDIs are not equipped with a dose counter. In order to track the number of doses remaining in the pMDI, patients can manually record the number of doses they have administered, shake the pMDI to determine the amount of medication remaining, or float the canister in water. None of these methods is reliable. It is estimated that only 8% of pMDI users accurately track the doses they administer. There exists a need for a pMDI system that will permit patients to accurately assess the amount of medication remaining in the canister. The present invention provides a pMDI system having a transparent canister to permit visualization of the amount of medication remaining. The present invention also provides a pMDI system equipped with a dose counter that is driven to count a dose when a dose is dispensed.